Background
He was born on November 11, 1875 near Mulberry, Indiana, United States, the son of Daniel Slipher, a farmer, and Hannah App.
He was born on November 11, 1875 near Mulberry, Indiana, United States, the son of Daniel Slipher, a farmer, and Hannah App.
He graduated from Frankfurt (Ind. ) High School. He then entered Indiana University, where he studied astronomy with Wilbur Cogshall, who had served as an assistant at the Lowell Observatory from 1896 to 1897. Slipher received a B. A. in mechanics and astronomy in 1901. He returned to Indiana on several occasions for graduate study, earning an M. A. in 1903 and a Ph. D. in 1909.
Slipher taught at a small country school nearby until the fall of 1897. Cogshall persuaded Percival Lowell to hire Slipher as a temporary assistant at the observatory in Flagstaff, Ariz.
Slipher's first task at the Lowell Observatory was to install a new spectrograph made by the famous Pittsburgh instrument-maker John A. Brashear. Lowell had ordered this instrument for research on extraterrestrial life. Slipher obtained estimates of planetary rotation periods and of the atmospheric composition of Mars and Venus, and also investigated stellar and nebular phenomena; this led in 1909 to the detection of interstellar gas and its absorption of light. He discovered that the diffuse nebula in the Pleiades shone solely by reflected starlight, indicating the existence of interstellar dust.
He began his investigations at the direction of Lowell, who thought that these bodies might represent evolving planetary systems. Lowell told Slipher to obtain spectral data from the nebulae to compare with those of the solar system. Although restricted to the observatory's twenty-four-inch refractor and forced to construct a suitable spectrograph from available parts, Slipher by 1912 had obtained several exposures of the Andromeda nebula (M31). These spectrograms convinced Slipher that the radial velocity of this nebula (now known to be a galaxy) could be calculated by comparing the position of spectral lines from M31 with the position of the same lines in a laboratory spectrogram. The Doppler shift of these lines would indicate the velocity and direction of the nebula's motion.
Slipher announced in February 1913 that the Andromeda nebula was approaching the earth at 300 kilometers per second, a velocity three times greater than that of any previously measured astronomical object. Over the next eighteen months, he calculated the radical velocities of fourteen other nebulae, finding that most were receding from the earth at velocities as great as 1, 000 kilometers per second. These discoveries provided crucial support for the work of the Dutch astronomer Willem de Sitter, who suggested in 1917 that the universe was expanding.
For the next decade Slipher continued to dominate research into nebular velocities. He was increasingly involved with administrative matters after Lowell's death in 1916. However, Slipher's work on the spiral nebulae soon ended. The Lowell Observatory's equipment could not record the details of the more distant and fainter nebulae, and such research passed to the Mt. Wilson Observatory with its 100-inch reflector. While measuring the radial velocities of nebulae, Slipher also examined their rotation.
By 1917 he had concluded that the spiral nebulae usually rotated in a manner similar to the winding of a spring. Slipher's theory challenged the earlier work of Adriaan van Maanen at Mt. Wilson, who had examined comparative photographs of spiral nebulae taken at short intervals and concluded that these nebulae were actually unwinding.
Although he remained a major figure in astronomy, Slipher was largely devoted to the administration of the Lowell Observatory after he assumed the directorship in 1926. He continued the observatory's planetary studies, including the work of his brother, Earl, who joined the staff in 1906.
After his retirement in 1954 Slipher worked in observatory and community affairs but pursued no further astronomical research. He died in Flagstaff.
Slipher married Emma Rosalie Munger on January 1, 1904; they had two children.